chromium/chrome/test/data/extensions/api_test/webrequest/cors/fetch.html

<!--
 * Copyright 2019 The Chromium Authors
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
-->
<script>
const params = (new URL(location.href)).searchParams;
const hostname = 'cors.example.com';
const origin = location.protocol + '//' + hostname + ':' + location.port;
const path = params.get('path');
const abspath = params.has('abspath') ? params.get('abspath') : undefined;
const url =
      origin + (abspath || ('/extensions/api_test/webrequest/cors/' + path));
const withPreflight = params.has('with-preflight');
const headers = withPreflight? {'x-foo': 'x-bar'} : undefined;

fetch(url, { headers, cache: 'no-store' });
</script>